The objective of this study was to investigate the long-term, low-concentration elution tailing of organic contaminants from a naturally heterogeneous (poorly sorted) aquifer material, with a specific focus on characterizing the relative contributions of rate-limited sorption/desorption, physical-heterogeneity-related processes, and rate-limited dissolution of nonaqueous phase liquids. The results obtained for the first component of this three-part study indicate (1) sorption of trichloroethene by the aquifer material was relatively small; (2) sorption/desorption of trichloroethene was found to be nonlinear and rate-limited, contributing to low concentration elution tailing; (3) the overall dispersion associated with the poorly sorted aquifer material was relatively large, also contributing to the tailing observed for the contaminant; and most interestingly, (4) trichloroethene elution curves obtained after significant flushing in the higher-fines aquifer material exhibited greater tailing than those obtained with minimal flushing, suggesting temporal variability of the porous medium dispersive properties. These changes appear to associated with the fines fraction of the aquifer material, and are possibly related to chemical weathering effects. This condition-dependent elution behavior has potentially significant ramifications for evaluating the transport behavior of contaminants in porous media, especially with regard to characterizing the nature and rates of mass-transfer processes. In the second part, the relative contributions of core-scale structuring versus those of rate-limited sorption/desorption to the observed nonideal transport of trichloroethene were examined. The results of these experiments were analyzed using a mathematical model incorporating multiple sources of nonideal transport. The results indicate that both physical and chemical factors, specifically rate-limited diffusive mass transfer associated with nonuniform flow conditions and rate-limited sorption, respectively, contribute to the nonideal trichloroethene transport observed for the undisturbed cores. In the third part, the long-term, low concentration elution behavior associated with dissolution of immiscible-liquid phase trichloroethene was investigated. The complete dissolution of trichloroethene was successfully simulated using a combined, multi process mathematical model. A comparison of these results to those discussed above suggests the low concentration elution tailing observed in the dissolution experiment is associated with rate-limited sorption/desorption. This study clearly indicates that multiple sources of nonideal transport behavior must be considered to fully and accurately characterize contaminant transport in the subsurface.

<p> The island of Puerto Rico, a commonwealth of the United States of America, has a population of 3,725,789 according to the 2010 census, and generates 11,100 tons daily of waste. In the Island, landfilling is the dominant form of waste disposal. Most municipal solid waste landfills (MSWLF) in Puerto Rico are a principal source of land, water, and air pollution. In addition, the scarcity of appropriate land to open new landfill facilities make this type of waste disposal an unsustainable form of waste management for the Island. </p><p> This study evaluated the current situation of the MSWLFs in Puerto Rico and the geographic limitations of continuing with this type of waste disposal on the Island. As alternatives to this problem, the principal waste-to-energy (WTE) technologies, combustion and gasification, are evaluated as environmentally responsible forms for disposal of non-recycled waste. </p><p> The evaluation methodology used is based on a multi-criteria decision-making model that uses a subjective rank-order weighting method. Evaluation of WTE technologies is performed by comparing dissimilar indicators in five interest areas: technical, economic, environmental, socio-political, and risk. The methodology is composed of two-components: an expert survey and data analysis. </p><p> An evaluation of the environmental interest area was performed to assess which of the WTE technologies studied herein, combustion or gasification, is more environmentally responsible. In addition, using the relevant scores in different interest areas, they were evaluated to determine the economic benefits of these WTE technologies as viable waste management alternatives for Puerto Rico.</p><p>

<p> Urbanization causes increases in impervious cover, alteration of stream channels, and introduction of pollution sources to waterways. Two rain gardens were installed at the headwaters of the Jenkintown Creek to combat urbanization effects and protect the stream from increased stormwater runoff, which can lead to higher flood peaks and pollution control problems. Thermal pollution found in urban runoff is a significant contributor to degradation of streams. Some fish such as the brown trout can be severely affected by heated runoff and many organisms lack the ability to regulate their body temperature. The goal of this research was to assess the thermal impacts from two rain gardens on the headwaters of the Jenkintown Creek from temperature surges during rainfall events. This goal was accomplished by analyzing two and half years of continuous data during non-winter months from a weather station and a flow meter located downstream of the rain gardens. The data from the weather station were precipitation and air temperature. The flow meter data included flow depth, velocity, and temperature. Three months of pre-construction data were collected before the first rain garden was installed. </p><p> The data analysis revealed that surges in water temperature of up to 3.3 &deg;C are found in the headwaters of the Jenkintown Creek almost immediately after it starts raining. A weak correlation (R² = 0.31) between the total water temperature change and studied storm intensity was found. Comparison of pre- and post-construction data showed that the median water temperature surge decreased by approximately 1 &deg;C after the installation of the first rain garden located approximately 315 meters upstream of the flow meter. The installation of the second rain garden located approximately 10 meters upstream of the flow meter did not cause a significant change in temperature surge. The cause of this decrease in temperature can be attributed to the transfer of heat from the hot runoff to the soils in the rain garden. Although a 1 &deg;C decrease of temperature surges is a small number, such a decrease can have a tremendous impact on cold water species such as the brown trout. </p><p> This research is part of the Delaware River Watershed Initiative (DRWI), funded by the William Penn Foundation (WPF).</p><p>

The inactivation of pathogens in sewage sludge reduces the risks of infection through contaminant pathways associated with handling and disposal. Domestic sludge sourced from a rural treatment plant was found to contain high levels of the indicator microoganisms E. coli and fecal coliforms and pathogenic bacteria Salmonella spp., Shigella spp., and C. perfringens. An effective and simple approach to enhance pathogen removal in a rural treatment setting was desired. Existing literature suggested that draw/fill staged configurations tended to yield better inactivation rates. Other literature suggested that the build-up of inhibitory compounds such as VFAs were detrimental to pathogens and that VFAs could be accumulated in higher temperature microaerobic conditions. The investigation of microaerobic pretreatment was trialed as a novel approach to staged digestion for improved pathogen removal. Microaerobic pretreatment of aerobically digested sludge improved inactivation of aerobic bacteria but the inactivation of persistent spores of C. perfringens were inconclusive. Microaerobic pretreatment alone was investigated in three phases of the experiments and did not result in inactivation greater than one log reduction for any bacteria monitored. In Phase I where feed solids concentration was varied across four reactors, the lowest solids loading of 1.1% TS showed the best removal rates of pathogens. In Phase II, contact time was evaluated in terms of feeding frequency and residence time. It was found that less frequent feeding and longer residence times were more effective in removing pathogens as expected from the reactor kinetics and suggested by the literature. The impact after digestion was found to be significant in Phase III for fecal coliforms, E. coli, Salmonella spp. and Shigella spp. It appeared that changes to the sludge matrix in microaerobic pretreatment improved digester performance in terms of pathogen removal. Operating variables were monitored to gain an understanding of the factors impacting performance. Statistical analyses were performed at the 90% confidence interval to determine which if any factors differed significantly between systems and stages. The major findings were that mesophilic pretreatment (35&deg;C) with air supplied at 0.06vvm yielded significantly higher ammonia levels after pretreatment than did pretreatment at ambient temperatures. This was hypothesized to account for the significantly greater extent of nitrification observed in downstream aerobic digestion over the effluents from digestion without pretreatment and those that were pretreated under ambient microaerobic conditions. Accordingly, the pH in those digesters was significantly lower than after digestion without pretreatment and after digestion with ambient microaerobic pretreatment. This enhanced depression in pH was hypothesized to account for the significantly enhanced inactivation in pathogens.

The Monod or hyperbolic kinetic formulation became the de facto kinetic descriptor in activated sludge models in the '80s-'90s. It still plays a prominent role in activated sludge models; however, a dual hyperbolic formulation (with respect to both substrate and active biomass) that implicitly accommodates storage as well as more rationally describes metabolic kinetics is more prominent in governing metabolic functions in activated sludge models (ASMs) promulgated by working groups under the aegis of the International Water Association (IWA). There are other kinetic formulations used in the models of this group as well as models of the activated sludge process formulated by others. There is lack of consistency in the choice of kinetic formulations for various processes even within the IWA family of models. This thesis examined the basis for the common Monod and dual-hyperbolic formulations and puts forward theoretical justifications of them based on various considerations of mass transfer, storage and metabolic rate formulation. Other models were developed based on major governing principles. Models used in biological wastewater treatment are Eulerian gross descriptors of a process involving mass transfer, many substrates, and metabolic pathways and their enzymes, contained within many microorganisms. Any model at this level is merely a fit of mathematical formulations to data. As number of processes in biotreatment models increases along with mathematical descriptors and their associated coefficients, fitting an overall model improves to a point. But beyond this there has been little justification of the Monod or other kinetic expressions. Since a variety of formulations have been proposed for two of the primary metabolic processes which are hydrolysis of complex substrates and then metabolism of resulting readily degradable (or simple) substrates, the primary objective of this study was to examine these processes by experiment and determine the most appropriate models for each step. A chemostat was used in this study to culture active biomass acclimatized to a feed containing starch, a complex substrate requiring hydrolysis, and glucose which is readily biodegradable and also a product of starch hydrolysis. Active mass samples were taken from the chemostat and placed in batch reactors where varying concentrations of active mass were exposed to varying concentrations of either glucose or starch. Before adding any substrate to the batch reactors the active mass was aerated for a period of time until DO change was not observed to ensure that any stored or extraneous substrate was metabolized. After addition of one or the other substrate, the rate of dissolved oxygen (DO) uptake was monitored over the initial 15 minutes in the batch culture. Rapidly changing conditions dictated the necessity of using DO as a surrogate for either starch or glucose. Over 249 models were examined for their ability to describe glucose metabolism for 16 different batch experiments. The Monod model gave a good fit to the data. Other models that were equally applicable were too complex or made no scientific sense. Another series of batch tests were conducted using only starch as a substrate. Again substrate concentration and active mass concentration were varied in the batch tests in six different batch runs. The results from these experiments were again used to determine the adequacy of 249 starch hydrolysis models. The Monod type relationship and a dual hyperbolic relation again proved to be the most reasonable choices. Also a first-order model based on starch concentration was applicable. However no general set of coefficients that applied to all experiments was found for any model; it is necessary to calibrate either model to environmental conditions. All of these models are fairly simple in terms of concept as well as determination of parameters and have scientific sensibility in describing hydrolysis of SBCOD. Keywords: wastewater, activated sludge, dissolved oxygen, modeling

Under anaerobic conditions, it is widely assumed that nitrate (NO3-) and nitrite (NO2-) reduction is primarily the result of microbial respiration (Burgin and Hamilton, 2007; Granger et al., 2008). However, it is also proven that the abiotic reduction of nitrate and nitrite by reduced iron(II) (Fe(II)), whether mineral-bound or surface-associated, may also occur under certain environmentally relevant conditions (Chao and Kroontje, 1966; Straub et al., 1996; Picardal, 2012,). With a range of experimental conditions, nitrogen and oxygen stable isotope systematics of abiotic nitrite reduction by Fe(II) were investigated in an effort to characterize the biotic and abiotic processes in the environment. While homogenous reactions between NO2- and Fe(II) in artificial seawater (ASW) showed little reduction, heterogeneous reactions involving Fe-containing minerals showed considerable nitrite loss. Specifically, rapid nitrite reduction was observed in experiments that included reduced nontronite clay and an Fe(II)-Fe(III) hydroxide mineral, termed green rust. These iron oxides and clay minerals offer both a source of reduced iron in the mineral matrix as well as a surface for Fe(II) activation. Additional control experiments with corundum as a non-Fe containing mineral surface showed little NO2- loss, implicating a more dominant role of structural iron in the clays during nitrite reduction. In experiments with nontronite and green rust the isotope effects (15ε and 18ε) ranged from 3 to 16‰ for 15ε and 2 to 6‰ for 18ε. Nitrite reduction rates and 15ε values within an experimental condition were directly correlated with slower reactions having higher isotopic fractionation. The apparent 18ε was affected by oxygen atom exchange with water, which lowered the isotope effect. Although little data exist for comparison with the dual isotopes of microbial NO2- reduction, these data serve as a benchmark for evaluating the role of abiotic processes in nitrogen (N) reduction, particularly in sediment systems low in organic carbon and high in reduced iron. / Engineering Sciences

<p> The primary goal for remediation of sediments contaminated with polychlorinated biphenyls (PCBs) is the reduction of bioaccumulation in the aquatic food web, particularly in fish that is the source of exposure to top level predators and humans. While empirical results are available in the literature on bioavailability reductions after amendment of PCB-contaminated sediment with a strong sorbent like activated carbon (AC) or biochar, there is a lack of quantitative understanding on how reductions in sediment porewater and food concentrations impact accumulation in fish. Although passive sampling can measure freely dissolved concentrations accurately, there is a major gap in the utilization of fate and biouptake models that can use such measurements. In addition, well-calibrated partitioning models based on accurate freely dissolved concentrations that can predict uptake by pelagic organisms are lacking. The primary objective of this research was to test the ability of frequently used bioaccumulation models to predict changes in fish uptake upon amendment of AC sediment and use passive sampling inputs and additional studies to refine the predictions made by these bioaccumulation models. </p><p> Results from laboratory exposure studies with pelagic and benthic feeding fish indicate that by incorporating changes in porewater and overlying freely dissolved PCB concentrations in kinetic bioaccumulation models and by taking into account changes in food concentration it is possible to predict effectiveness of sediment remediation in reducing PCB uptake in fish. Assimilation efficiency of PCBs in the sediment were independently measured in a separate study and incorporated into the model. The modified model led to reasonable estimations of PCB uptake in the benthic feeding fish and was capable of predicting the dominant exposure pathways in the benthic and pelagic feeding fish as a result of their different feeding behaviour. Additionally, passive sampling measurements were linked to PCB accumulation in algae and zooplankton and resulted in refined models. Lastly, several scenarios were simulated to show the potential of a linked fate and biouptake model to capture the effect of different inputs. </p><p> This research presents a robust modeling framework that is able to predict uptake in fish after <i>in situ</i> remediation that alters bioavailability of PCBs in sediments with implications for risk assessment and management.</p><p>

Land application of biosolids is a desirable solution for smaller communities that utilize aerobic digestion. However, traditional aerobic digestion produces Class B biosolids at best which raises public concern regarding the fate of pathogens following land application. The main goal of this work was to determine a plan to help an aerobic digestion WWTP achieve improved pathogen destruction. An approach of studying the effect of a pre-treatment step prior to digestion was developed following site visits to eight aerobic digestion facilities in Ontario. The experimental phases of this work evaluated the effect of aeration rate, temperature and retention time on pathogen reduction in 12 setups. The four best conditions were carried out with digestion to evaluate the ultimate impact of pre-treatment on digestion. The results indicated that a micro-aerobic, highly reducing environment produces adverse conditions within the pre-treatment column which also impact subsequent digestion and resulted in decreased pathogens.

Pretreatment of primary sludge, waste activated sludge, and comingled sludges has become of substantial interest for the improvement of the rate limiting hydrolysis step during anaerobic digestion. As primary sludges are already easily degraded, waste activated sludges provide the most noticeable improvements in anaerobic digestion (AD) as a result of sludge pretreatment (SPT). A vast literature and theory review was conducted to establish high-potential treatment and result ranges. The average wastewater compositions for total chemical oxygen demand (COD) and total solids (TS) were 16-43 and 13-40 g/L, respectively. Sludge pretreatment percent solids solubilisation ranges for all common SPT technologies were 13-42% for both particulate COD and total suspended solids (TSS). Subsequent anaerobic digestion enhancement ranges were percent reductions in total COD and TS of 24-55 and 22-46%, respectively, as well as biogas production increases of 9-43%. The ranges shown here were fairly representative of those observed for all SPTs. Additional SPT technology information for full-scale design was also gathered. A MS Excel spreadsheet wastewater treatment plant model (referred to herein as PretrAD) capable of comparing control and SPT incorporation scenarios was created. The PretrAD output was verified against a third party commercial model. PretrAD allows the user to input data on performance of all unit processes found in a typical biotreatment wastewater treatment plant (WWTP). Various return flow paths and other attributes of a WWTP can be specified and provide versatility and comprehensiveness. A database of typical performance data for all unit processes was compiled and used in PretrAD and for comparing performance of WWTPs with and without SPT. The stirred ball mill, high pressure homogenizer, and ultrasound technologies were mechanical processes with sufficient comparable data for inclusion in PretrAD. Conventional heating and microwave heating technologies were included as thermal processes. Alkaline and ozone technologies were included as chemical processes. Finally, the common conventional heating + alkaline (thermochemical) technology was also included alongside a purely financial assessment of a proposed microwave heating + alkaline technology incorporation scenarios. PretrAD was then used to evaluate treatment benefits by varying a number of performance parameters with and without SPT. Operating parameters that were changed were normal and low heat recoveries at the anaerobic digester, normal and doubled sludge disposal distances, low-peak influent flow regimes, and low to high SPT energy demands (evaluated with identical solubilisation results). Control and SPT scenarios were performed for all variables and both mesophilic and thermophilic AD. Overall net WWTP treatment costs based on energy inputs and recoveries along with chemical inputs were compared for the various scenarios. It was found that an all average influent flow regime represented (within 5%) all annual flow regime combinations of low, average, and high flows and their associated quality variations. Following the basic comparisons of control and SPT scenarios, additional runs were conducted with increases of 25 and 50% for the energy demands of each SPT. Mesophilic AD scenarios always had lower final costs than thermophilic AD scenarios under identical treatment parameters. Practical (cost-effective) and impractical (higher than control costs) scenarios were found for all SPTs except thermal and thermochemical processes. Thermal and thermochemical processes were always practic31 and always impractical, respectively, when compared to control scenarios using identical conditions. When different scenario conditions were compared, both thermal SPTs were deemed impractical when high cost results were compared to low cost results. Solids loadings and heat recoveries were the most cost-influential variables of PretrAD. Other important qualitative results were not incorporated into the evaluation. They include but are not limited to dewatering improvements, pathogen reduction, anaerobic digester vessel size reduction, and hydraulic residence time reductions for the anaerobic digester. Inclusion of these parameters could render some SPTs practical for scenarios where they were deemed impractical on a pure cost of treatment basis. Furthermore, full-scale incorporation drawbacks such as additional unit costs, operation and maintenance demands, and actual throughput capacities could render some practical scenarios impractical. The constructed PretrAD model has been proven effective for the rapid determination of treatment plant costs related to SPT incorporation. A tool such as this is vital for the site-specific analysis of SPT technologies.

Improvement of biodegradability of waste activated sludge (WAS) depends on enhanced disintegration of the floc structure of sludge and increasing the accessibility to both intracellular (within the microbial cell) and extracellular (within the polymeric network) materials before WAS is sent to anaerobic digesters. This study proposes microwave (MW) technology as a new and an alternative pretreatment method to disintegrate the floc structure of secondary sludge, to enhance the hydrolysis and to improve the anaerobic digestion of WAS in comparison to existing pretreatment methods such as, chemical, mechanical and conventional heating (CH) techniques. In the first stage of the study, the effects of MW pretreatment on disintegration and hydrolysis of WAS by soluble chemical oxygen demand (COD), soluble protein, soluble sugar and nucleic acid leakage detection experiments were investigated. The effects of three variables [MW temperature (T), MW intensity (I), WAS concentration (C)] and the effects of four variables [T, I, C and volume percentage of WAS pretreated (PT)] were investigated on WAS solubilization and biogas production in two multilevel factorial statistical designs containing 24 solubilization runs and 54 mesophilic batch reactors, respectively. In a low temperature range (50-96&deg;C) using a household type (1250 W, 2450 MHz) MW oven, pretreated WAS samples resulted in 3.6 +/- 0.6 and 3.2 +/- 0.1 fold increases in soluble COD/total COD ratios at high [5.4% total solid (TS), w/w] and low (1.4% TS, w/w) sludge concentrations, respectively. WAS, pretreated to 96&deg;C, produced the greatest improvement in biogas production with 15 +/- 0.5 and 20 +/- 0.3% increases over the controls (unpretreated) after 19 d of digestion at low and high WAS concentrations. In the second stage of the study, two different pretreatment temperatures (50 and 96&deg;C) were further tested in a total of 10 semi-continuous digesters at sludge retention times (SRTs) of 5, 10 and 20 d. Digesters using CH WAS were also run to investigate thermal and athermal effects of MW pretreatment. In general, incremental increases in total solid (TS), volatile solids (VS) and total COD removal efficiency of pretreated digesters compared to controls dramatically increased as SRT was gradually shortened from 20 to 10 to 5 d. WAS pretreated to 96&deg;C by MW and CH achieved 29 and 32% higher TS and 23 and 26% higher VS removal efficiencies compared to controls at SRT of 5 d, while similar reactors at SRT of 20 d had only 16% higher TS and 11 and 12% higher VS removals than those of controls, respectively. Ultrafiltration (UF) was also used to characterize the soluble molecular weight (Mw) distributions of control, CH and MW irradiated WAS at 96&deg;C. Soluble CODs of CH and MW irradiated WAS were 361 +/- 45 and 143 +/- 34% higher and resulted in 475 +/- 3 and 211 +/- 2% higher cumulative biogas productions relative to the control at the end of 23 days of mesophilic batch anaerobic digestion, respectively. Depending on the Mw fraction, the range of substrate volumetric utilization rate increases from anaerobic digesters was between 94-184% for the CH and 26-113% for the MW compared to the control for the first 9 days of the digestion. Digesters treating high Mw materials (Mw > 300 kDa) resulted in smaller first-order biodegradation rate constants, k, indicating that microorganisms require a longer time to utilize high Mw fractions which are most likely the cell wall fragments and exopolymers. MW studies under the boiling point (100&deg;C at 1 atm) have promised a significant potential to disintegrate the floc structure and to enhance the hydrolysis and biodegradability of WAS in full-scale digesters.